ACC timing primer: what the numbers mean

PaceBoss works with one specific data source: a SimResults CSV export of an Assetto Corsa Competizione race or qualifying session. If you're new to ACC data, this page explains what that file contains, what the timing terms mean, and how PaceBoss uses them — before you encounter them in the tool.

The data source: SimResults

SimResults is a third-party tool that parses the result files ACC generates after each session. When you upload an ACC result file to SimResults and click Export CSV, you get a structured spreadsheet of every lap, every split, and every driver in that session.

PaceBoss reads that CSV. It does not connect to ACC directly, and it does not require any ACC companion app. The workflow is: race in ACC → process the result through SimResults → export a CSV → import that CSV into PaceBoss.

Sectors: S1, S2, S3

Every ACC track is divided into three timing sectors. A sector is a portion of the lap with its own checkpoint. When you cross a sector checkpoint, your time for that sector is recorded.

• S1 is measured from the start/finish line to the first sector checkpoint.
• S2 is measured from the first checkpoint to the second.
• S3 is measured from the second checkpoint to the start/finish line.

The three sectors sum to the lap time (for valid laps). Sector splits tell you where in the lap you gained or lost time relative to another driver — PaceBoss surfaces this as the three thermometers in the SectorsChip on the driver page.

Valid laps vs invalid laps

Not every lap counts toward the timing board. A lap is invalid if ACC marked it as a track-limits infringement (a "cut") that disqualifies the time. PaceBoss displays invalid laps in the laps table with an INV badge and excludes them from best-lap calculations.

PaceBoss also flags pit laps — any lap whose time exceeds 1.5× the driver's median lap time. SimResults doesn't tag pits explicitly, so this is an inference. Pit laps are excluded from consistency calculations.

Cohort

A cohort is the group of drivers a given driver is compared against. In a single-class race, the cohort is the entire field. In a multi-class race — a GT3 and GT4 grid sharing the same session, which is common in ACC — the cohort defaults to your class only.

This matters because a GT4 driver isn't 10 seconds off pace just because GT3 cars exist. When PaceBoss says "you're 0.3 seconds off the cohort's best in S2," it means 0.3 seconds off the fastest S2 among the drivers in your class — unless you've switched the cohort toggle to overall, in which case it means 0.3 seconds off the fastest S2 in the entire field.

What's in the CSV (and what isn't)

PaceBoss reads:

• Per-lap totals (lap time, validity flag, lap number)
• Per-sector totals (S1, S2, S3 split times for each lap)
• Session metadata (track, session type, date, server)
• Per-driver entry data (car number, car model, class, team, finish position, gap to leader, best lap)

PaceBoss does not have access to telemetry — there is no brake pressure, throttle position, steering angle, speed trace, or car-attitude data in a SimResults CSV. The tool works with what the CSV contains and is explicit about that boundary. See what PaceBoss can and can't tell you for the full scope.

Where to go next

• How PaceBoss works — the full app walkthrough, view by view.
• Glossary — every term PaceBoss uses, with how each value is computed.
• Find your pace deficit — the first practical workflow for using your race data.